Free radical scavenging compounds are those which bind, typically harmful free radicals that are generated as by-products of reactions. These compounds are generally known in the art. Examples of commonly used free radical scavengers include butyl hydroxy toluene (BHT), butyl hydroxyanisole (BHA), tertiary butyl hydroquinone (TBHQ), non-tert buty; hydroquinone (MTBHQ), ascorbic acid, propyl gallate.
Radical scavengers can be used in a number of applications to bind free radicals, for example in medicine as an antioxidant, in the preservation of fuels and foods and to stabilise bleaching compositions. By the term free radical it is meant fragments of molecules having one or more unpaired electrons for example .Cl, .OH, .ClO and carbon-centered free radicals like .CR(R′)(R″) and benzene derived free radicals. The Applicants have developed a new radical scavenging compound which provides at least parity, but more often improved binding of free radicals versus radical scavengers currently available in the art, for example butyl hyroxy toluene (BHT) and those other radical scavengers listed above.
Bleaching compositions comprising either an oxygen-releasing or a hypohalite-releasing bleaching agent can become unstable and loose bleaching power over time. This is possibly due to the reaction of the bleaching agent with heavy metal ions present as impurities in, for example raw materials or water. This reaction results in the decomposition of the bleaching agent and the release of free radicals. The free radicals present in bleaching compositions are intensely reactive and it is believed, further catalyse the decomposition of the bleaching agent. The Applicants have found that by inclusion of the free radical scavenger of the present invention in a bleaching composition, the stability of the composition over time is improved. In fact the radical scavenger of the present invention provide parity or improved radical scavenging versus for radical scavengers currently available in the art, for example butyl hyroxy toluene (BHT) and those other radical scavengers listed above in bleaching compositions.
Furthermore, free radicals are also believed to be detrimental to the integrity of the surface being bleached, for example a fabric. It is believed that the free radicals initiate a reaction of the fabric fibers themselves. An example of which is the oxidation of free hydroxide groups of cotton fibers contributing to the degradation and premature aging of the fabric. Fabric degradation and premature aging are most often identified by a loss of whiteness of the fabric. Hence it is a further advantage of the present invention that fabric whiteness can be maintained or improved by washing the fabric with compositions as described herein.
Further still, it has also been found that the radical scavenger compound of the present invention is a useful tool in detecting the presence of free radicals in any application not limited to cleaning compositions. Thus in a further aspect of the present invention is defined a test method for detecting free radicals by measuring the intensity of a colour change.